(1) Field of the Invention
The present invention relates to an electric contact structure, which is provided in an electronic instrument mounted on a motor vehicle as a mobile unit and is used, for example, to ground a movable part of the electronic instrument, to a process for producing the electric contact structure, and to an electronic instrument having the electric contact structure.
(2) Description of the Related Art
A car stereo (for example, see Japanese Patent Application Laid-Open No. H10-51712) as an electronic instrument is mounted on an instrument panel of a motor vehicle as a mobile unit. The car stereo includes: a body of the car stereo to be mounted on the instrument panel; and a front panel as a movable part, which has a display, such as liquid crystal display, and various operation buttons.
The instrument body (i.e. body of the car stereo) includes a CD player, MD (mini-disc) player, DVD-ROM player for constituting a navigation system and so on. The front panel displays information such as map information in the navigation system and information indicating playback situation of a CD player and MD player on a liquid crystal display or the like. The front panel is provided with a touch switch and push button to be operated when the navigation system, CD player or MD player is driven.
In order to restrict a space for mounting the car stereo to the instrument panel, a face (hereinafter, front face) facing a user of the instrument body is provided with an insertion opening through which the CD player, MD player and DVD-ROM player can be taken into and out from the instrument body. Further, in the car stereo, the front panel is set slidably movable over the range from a position for shielding the front face to a position for opening at least a part of the front face. Therefore, the front panel is attached to the instrument body partially having a small gap therebetween.
The car stereo positions the front panel at a position where at least a part of the front face of the instrument body is opened and then, the CD player, MD player and DVD-ROM player are taken into and out from the instrument body. After the CD player, MD player and DVD-ROM player are inserted into the instrument body, the front panel is shifted to a position for shielding the front face and then, the operation button such as a touch switch and various push buttons are operated so as to drive the CD player, MD player and DVD-ROM player. The information indicating the playback situation of these players is displayed on a liquid crystal display or the like.
In the conventional car stereo, the front panel is set slidably movable over the range from a position for shielding the front face to a position for opening at least a part of the front face. The static electricity might be charged on the front panel of the car stereo. Therefore, in the conventional electronic instrument, in order to remove the static electricity out from the electronic instrument, various electric contact structures (hereinafter, ground structures) for electrically connecting the movable part, such as the front panel, to the instrument body have been used so far.
Further, since the front panel is shifted as described above and therefore exposed to the outside, a sheet metal attached on the front panel is subjected to plating or coating for maintaining its fine sight. Therefore, the sheet metal has an electrically conductive base material and a surface layer formed on a surface of the base material by means of plating or coating. The surface layer is electrically insulating having a significantly larger electrical resistance than that of the base material.
Therefore, in the ground structure as described above, an electrically conductive sheet metal member, such as a sheet metal of the instrument body, to be attached to a chassis is made come in contact with the base material of the sheet metal to be attached on the front panel or the like. When the front panel is shifted, the sheet metal member and the base material of the sheet metal slide with each other, so that they are kept being electrically connected to each other. That is, in the ground structure as described above, the sheet metal member and the base material of the sheet metal are electrically connected to each other. That is, in the ground structure, the front panel and the instrument body are electrically connected to each other.
In the ground structure, when the sheet metal member and the base material of the sheet metal are electrically connected to each other, for example, a part of the surface layer of the sheet metal is removed by grinding. That is, the sheet metal member is made come in contact with thus exposed base material of the sheet metal. Alternatively, in the ground structure, the sheet metal member is made come in contact with the base metal exposed at an end face of the sheet metal. Thus, in the ground structure, the sheet metal member and the base material of the sheet metal are electrically connected to each other.
In the ground structure as described above, the removal of the surface layer by grinding or the like might cause increase in man-hour, that is, increase in cost of the electronic instrument. Further, since the grinding or the like is needed, the production yield might be deteriorated caused by excess grinding of the surface layer of the sheet metal.
Furthermore, when the sheet metal member is made come in contact with the base material exposed at the end face of the sheet metal, the end face of the sheet metal, which becomes rough due to burrs or the like, is scraped by the sheet metal member. Therefore, when the front panel is shifted as described above, a noise might occur.